TJs have been observed by the freeze-fracture electron microscopy as the network of intramembranous strands (TJ strands) , formed by the assembly of claudins
and TJ-associated myelin and lymphocyte protein and related proteins for vesicle trafficking and membrane link (MARVEL) proteins.
The most important TJ proteins in the intestinal mucosa are ZO-1, occludin, and claudins
, and the expression of all 3 in the intestine are decreased by infection with ETEC K88 [24, 30].
Tight junctions have several membrane and cytoplasmic proteins  ; some of these such as occludins, claudins
, and zona occludins (ZO proteins) have been well studied [34-38].
in intestines: distribution and functional significance in health and diseases," Tissue Barriers, vol.
Loss of function in filaggrin and deficiencies in loricrin, involucrin and claudins
lead to epidermal barrier disruption causing transepidermal water loss and xerosis.
Arsenic treatment of primary mouse tracheal epithelial and immortalized human bronchial epithelial cells reduces transepithelial electrical resistance, a measure of barrier function, and also alters expression of claudins
(Sherwood et al.
Different molecules have been identified as the components of TJ such as transmembrane protein claudins
, occludin, and peripheral membrane protein zonula occludens (ZO).[sup] Abundant studies showed that claudin-5, a major determinant of the properties of the endothelial barrier, played an important role in the blood-brain barrier and blood–retina barrier.
Recent studies revealed the existence of another subtype, the claudin-low subtype, (22) characterized by down-regulation of tight junction proteins including E-cadherin, occludin, and some claudins
, and by high expression of genes associated with epithelial-mesenchymal transition (EMT), immune response, and the breast cancer stem-cell phenotype.
The tight junctions are composed of transmembrane proteins, including occludin, claudins
, tricellulin and junctional adhesion molecules, which may interact with the scaffold proteins such as ZO-1, ZO-2, ZO-3, etc to form the macromolecular compounds and anchor to the actin cytoskeleton on the membrane surface of the adjacent epithehal cells .
Furuse, "The structure and function of claudins
, cell adhesion molecules at tight junctions," Annals of the New York Academy of Sciences, vol.
Formation of both tight and adherens junctions requires proper localization and assembly of ZO-1 scaffolding prior to recruitment of transmembrane proteins such as occludin or claudins